ABSTRACT
In ovarian cancer, the prometastatic RTK AXL promotes motility, invasion and poor prognosis. Here, we show that reduced survival caused by AXL overexpression can be mitigated by the expression of the GPI-anchored tumour suppressor OPCML Further, we demonstrate that AXL directly interacts with OPCML, preferentially so when AXL is activated by its ligand Gas6. As a consequence, AXL accumulates in cholesterol-rich lipid domains, where OPCML resides. Here, phospho-AXL is brought in proximity to the lipid domain-restricted phosphatase PTPRG, which de-phosphorylates the RTK/ligand complex. This prevents AXL-mediated transactivation of other RTKs (cMET and EGFR), thereby inhibiting sustained phospho-ERK signalling, induction of the EMT transcription factor Slug, cell migration and invasion. From a translational perspective, we show that OPCML enhances the effect of the phase II AXL inhibitor R428 in vitro and in vivo We therefore identify a novel mechanism by which two spatially restricted tumour suppressors, OPCML and PTPRG, coordinate to repress AXL-dependent oncogenic signalling.
Subject(s)
Cell Adhesion Molecules/metabolism , Ovarian Neoplasms/metabolism , Proto-Oncogene Proteins/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Receptor-Like Protein Tyrosine Phosphatases, Class 5/metabolism , Tumor Suppressor Proteins/metabolism , Animals , Benzocycloheptenes/pharmacology , Cell Line, Tumor , Cell Movement/drug effects , Cell Survival/drug effects , Chickens , Cholesterol/metabolism , Enzyme Activation/drug effects , Epithelial Cells/drug effects , Epithelial Cells/metabolism , Epithelial Cells/pathology , Fallopian Tubes/pathology , Female , GPI-Linked Proteins/metabolism , Gene Silencing/drug effects , Humans , Intercellular Signaling Peptides and Proteins/metabolism , MAP Kinase Signaling System/drug effects , Membrane Microdomains/metabolism , Neoplasm Invasiveness , Ovarian Neoplasms/pathology , Phosphorylation/drug effects , Protein Binding/drug effects , Treatment Outcome , Triazoles/pharmacology , Axl Receptor Tyrosine KinaseABSTRACT
Adeno-associated virus vectors (AAV) show promise for liver-targeted gene therapy. In this study, we examined the long-term consequences of a single intravenous administration of a self-complementary AAV vector (scAAV2/ 8-LP1-hFIXco) encoding a codon optimized human factor IX (hFIX) gene in 24 nonhuman primates (NHPs). A dose-response relationship between vector titer and transgene expression was observed. Peak hFIX expression following the highest dose of vector (2 × 10(12) pcr-vector genomes (vg)/kg) was 21 ± 3 µg/ml (~420% of normal). Fluorescent in-situ hybridization demonstrated scAAV provirus in almost 100% of hepatocytes at that dose. No perturbations of clinical or laboratory parameters were noted and vector genomes were cleared from bodily fluids by 10 days. Macaques transduced with 2 × 10(11) pcr-vg/kg were followed for the longest period (~5 years), during which time expression of hFIX remained >10% of normal level, despite a gradual decline in transgene copy number and the proportion of transduced hepatocytes. All macaques developed serotype-specific antibodies but no capsid-specific cytotoxic T lymphocytes were detected. The liver was preferentially transduced with 300-fold more proviral copies than extrahepatic tissues. Long-term biochemical, ultrasound imaging, and histologic follow-up of this large cohort of NHP revealed no toxicity. These data support further evaluation of this vector in hemophilia B patients.
